555 audio oscillator Analog Integrated Circuits


Posted on Feb 5, 2014

The 555 integrated circuit is a general-purpose timer useful for a variety of functions. In this experiment, we explore its use as an astable multivibrator, or oscillator. Connected to a capacitor and two resistors as shown, it will oscillate freely, driving the LEDs on and off with a square-wave output voltage. This circuit works on the princip


555 audio oscillator Analog Integrated Circuits
Click here to download the full size of the above Circuit.

le of alternately charging and discharging a capacitor. The 555 begins to discharge the capacitor by grounding the Disch terminal when the voltage detected by the Thresh terminal exceeds 2/3 the power supply voltage (Vcc). It stops discharging the capacitor when the voltage detected by the Trig terminal falls below 1/3 the power supply voltage. Thus, when both Thresh and Trig terminals are connected to the capacitor`s positive terminal, the capacitor voltage will cycle between 1/3 and 2/3 power supply voltage in a "sawtooth" pattern. During the charging cycle, the capacitor receives charging current through the series combination of the 1 M © and 100 k © resistors. As soon as the Disch terminal on the 555 timer goes to ground potential (a transistor inside the 555 connected between that terminal and ground turns on), the capacitor`s discharging current only has to go through the 100 k © resistor. The result is an RC time constant that is much longer for charging than for discharging, resulting in a charging time greatly exceeding the discharging time. The 555`s Out terminal produces a square-wave voltage signal that is "high" (nearly Vcc) when the capacitor is charging, and "low" (nearly 0 volts) when the capacitor is discharging. This alternating high/low voltage signal drives the two LEDs in opposite modes: when one is on, the other will be off. Because the capacitor`s charging and discharging times are unequal, the...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Over Voltage Protection
    Speech Recorder (ISD2560)
    Infinite sample and hold amplifier
    Schematic Diagram 250mW FM transmitter electronic circuit
    rf digital
    2ChPre
    Schematics USB Sound Card with PCM2702 PCB
    High Voltage Generation For Xenon Tube Applications
    It uses NAND gate transistor and humidity control circuit
    Composition equalizer with TA7796



    Top